All-Star Superman
Superman: Birthright
Superman: Kingdom Come
Action #775 "What's so funny about truth, justice and the American way?"
Superman #247 (iirc) "Must there be a Superman"
Whatever Happened to the Man of Tomorrow?
Superman: Red Son
Superman: Death and Return Saga
Superman: For the man who has everything
Superman: For All Seasons

A lot of the great ones were already mentioned but yeah get Exile or Ending Battle instead of Our Worlds At War IMO. Way better post-crisis Superman stories. Same with Panic in the Sky, Time and Time Again and Krisis of the Krimson Kryptonite.Escape from Bizzaro World, Up, Up and Away and Brainiac are all solid.Kryptonite is a great early Superman retelling that is often overlooked.

Adding to those I'd highly recommend Mark Millar's Superman Adventures work which is available in trades. If you don't mind reading older stuff Superman in the 70'sis another good one. The Black Ring is a Lex Luthor story but it's fantastic in every way. If you get Death and Return don't skip World Without Superman as IMO those were the best moments from the whole event.

In the case of Batman his in the 70's collection is also awesome. Batman: Ego, Batman and The Mad Monk and Gothic I would also say are really worth the time. Can't go wrong with Night Cries, The Black Mirror, Blind Justice or the Vampire Elseworlds stories either.

__________________I enjoy comic book adaptations but I'm a comic book fan first and foremost. Not a comic book movie fan.

Superman: Last Son
Superman: Earth One
Superman: For Tomorrow
Superman: Brainiac
Superman: President Luthor (the whole collection including when Lex found out Clark is Superman)
Superman: Up,Up and Away
Superman/Batman: The Search for kryptonite
Superman/Batman: World's Finest
Superman/Batman: Supergirl

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The Miraculous Return of Jonathan Kent
When Lightning Strikes, Thunder Kills
The Girl in Superman's Past!
Must There Be A Superman?
Luthor's Last Stand
Disappearing Act
How to make a marshland monster
The Miracle Man of Easy Company
Plague of the Antibiotic Man
The Super-Sons Saga
Superman vs. The Archer
I Can't Go Home Again
The Challenge of the Terra-Man
Luthor's Last Stand
Make Way for Captain Thunder
The Dying days of Lois and Lana!
Exile

I am actually planning on re-reading and reviewing all Batman stories going on from Batman #217, but I am not really sure if I should include stuff like JL, Brave & The Bold, World's Finest... And I also want to do the same with Superman...

I think Superman/Batman Apocalypse and Absolute Power (the 2nd and 3rd story arcs respectively from that series) were great too. Apocalypse was made into an animated movie and I feel that the other would make a good movie as well.

__________________" Again you seek to play the hero, little madman. Again you pay the price!"

Almost all the best Superman stories are single issues stories from the 60's and 70's and DC has distanced themselves from that Superman since they cannot even approach it's level of success. The character has been basically dead since 1986. Check out All-Star Superman for the closest thing since then to the real thing-but even it's nowhere as good.

Look for anything old written by Elliot Maggin, Jerry Siegel, Cary Bates or Otto Binder and that is the best Superman stuff.